Catalyst reactivation in the hydrogenation of phenol to cyclohexanol



CATALYST REACTIVATION IN THE HYDROGEN ATKUN F PHENOL T0 CYCLOHEXANOL Leon 0. Winstrom, East Aurora, N. Y., assignor to Allied Chemical & Dye Corporation, New York, N. Y., a can poration of New York No Drawing. Application January 19, W56, Serial No. 560,056

Claims. (Cl. 260-631) This invention relates to the conversion of phenol to cyclohexanol, and more particularly refers to a new and improved method of catalytically hydrogenating phenol in the liquid phase to cyclohexanol.

Cyclohexanol is an important industrial chemical which is used in the manufacture of intermediates for synthetic resins and polymers. Commercially, cyclohexanol is produced by hydrogenation of liquid phenol in the presence of a nickel catalyst. The process may be carried out by passing hydrogen gas into a body of molten phenol containing a suspended nickel-silica catalyst at elevated temperature and pressure until conversion to cyclohexanol is effected, as more fully described in my co-pending application entitled Cyclohexanol, Serial No. 554,654, filed December 22, 1955. As is common in catalytic reactions, the activity of the nickel catalyst deteriorates by use in liquid phase hydrogeneration of phenol with resultant impairment of product quality and reduced rate of reaction necessitating relatively frequent replacements with fresh catalyst.

An object of the present invention is to provide a method for reactivating nickel catalysts in the liquid phase hydrogenation of phenol to cyclohexanol.

Another object of the invention is to provide a method for greatly extending the effective operating life of the nickel catalyst in the liquid phase hydrogenation of phenol to cyclohexanol.

A further object of the invention is to provide a method for maintaining high yields of high quality products for prolonged periods in the liquid phase hydrogenation of phenol to cyclohexanol. Other objects and advantages of the present invention will be apparent from the fol lowing description.

I have discovered that a nickel catalyst, whose activity has deteriorated by use in liquid phase hydrogenation of phenol, can be reactivated in simple manner by the addition of small amounts of a metal salt of a surface active compound containing 6-30 carbon atoms, said salt having the general formula:

1 (O)=%O M O I wherein R isan organic radical selected from the group consisting of hydrocarbon radicals and substituted hydrocarbon radicals, x is 1 or 0, M is a member selected from the group consisting of Ni and Ag, and It stands forv I States Patent 0 Ice ducted in a batch sequential manner employing one or more enclosed hydrogenation vessels, for example having a capacity of approximately 20,000 pounds of phenol, each equipped with stirrers for agitating the contents. The amount of hydrogenation catalyst based on the amount of phenol charge is not critical and may be varied over a wide range. In practice we have carried out successful hydrogenation with from 2% to about 10% nickel catalyst, preferably within the range of 4-6% catalyst by weight of phenol. The hydrogenation reaction is carried out at a temperature between about 200 0, preferably within the range of -180 C. The hydrogenation reaction may be carried out under atmospheric pressure but use of superatmospheric pressure shortens reaction time. The reaction may be conveniently carried out at a pressure within the range of 20-250 p. s. i. g. Still higher pressures would be advantageous but large capacity equipment capable of withstanding such pressures is excessively costly. During the reaction pure hydrogen gas need not be employed to effect hydrogenation of the phenol and a gas containing hydrogen, such as a mixture of hydrogen and an inert gas such as nitrogen, may be employed. Hydrogen is introduced into the body of phenol until further hydrogenation substantially ceases as indicated by cessation of hydrogen absorption. After hydrogenation of a batch of phenol is completed, agitation is discontinued and the batch allowed to settle out. The catalyst settles to the bottom as a compact layer containing about 20% of the total cycloheXanol product. The rest of the product is a clear supernatant liquid layer which may be readily decanted. To the residual catalyst layer in the hydrogenation vessel is added a fresh batch of phenol and agitation and hydrogenation of the phenol accomplished in the manner as just described. The time required to complete the hydrogenation of phenol to cyclohexanol depends upon numerous variables: catalyst activity, temperature, pressure, cooling, heat transfer, agitation, etc.

The following is a description of a continuous operation employing a multivessel system. The first of a series of agitator-equipped hydrogenation vessels is continuously charged with molten phenol and a concentrated slurry of catalyst, or a pro-formed mixture of molten phenol and a concentrated slurry of catalyst. At the pared by slurrying catalyst in phenol or cyclohexanol; subsequently it is a slurry of catalyst in cyclohexanol which is separated from the eflluent stream from the last of the series of hydrogenation reactors and recycled as feed material to the first hydrogenation reactor. The reaction medium containing suspended catalyst overflows from one reactor into a conduit, which carries it (via a pump, if necessary) into the lower part of the next reactor down stream. The phenol is reacted with hydrogen in each reactor at elevated temperatures and pressures. Eflluent from the last hydrogenation reactor passes continuously through a separator, such as a cream-separator type centrifuge, which separates a catalyst-free product consisting of substantially pure cyclohe'xanol from a concentrated slurry of catalyst in cyclohexanol, which slurry is recycled as a feed stream to the first reactor. The activity of the hydrogenation catalyst will depend on the extent of use, which in batch operation would be the number of times the catalyst has been used, that is, fresh catalyst is usually more active than catalyst which has been used a number of times. The catalyst cannot be thus reused indefinitely before its activity declines (apparently by poisoning) to a point that it cannot be furthe catalyst is discarded. I have discovered that a nickel catalyst, whose activity has deteriorated by use in liquid phase hydrogenation of phenol, can be reactivated in simple manner without isolation from the reaction mixmm by addition of a small amount of nickel and silver compounds of the present invention. 1 have further discovered that a nickel catalyst may be reactivated repeatedly by the process of my invention whenever its activity declines excessively in such liquid phase hydrogenations, thereby making it possible greatly to extend the operating life of the catalyst, maintaining a high catalyst activity level and high product quality. The amount of additive needed to maintain or restore catalyst activity may be as low as 0.01% by weight of the total phenol charge and generally quantities up to 1.5% additive will be found adequate to restore catalyst activity, although larger amounts of additive may be employed if desired. The addition of additive may be accomplished simply by adding the additive directly to the catalyst slurry or to phenol, which is then admixed with the catalyst, or to a mixture of phenol containing suspended catalyst, or, if desired, the additive may be added to the catalyst by means of another liquid vehicle such as cyclohexanol. Upon the addition of the additive the nickel catalyst is restored to about its original activity and will continue at a high rate of activity for several successive batch hydrogenations without further addition of additive. After a second drop in activity of the catalyst, restoration of the catalyst may again be accomplished by a further addition of a small amount of additive.

The following examples illustrate the present invention and demonstrate its advantages.

EXAMPLE 1 The following is a description of a large-scale operationinvolving production of cyclohexanol' by catalytic hydrogenation of phenol inwhich a nickel catalyst deteriorated by use in hydrogenationof phenol was restored to high activity by addition of a small amount of additive in accordance with the present invention.

The nickelphenol hydrogenation catalyst was prepared as follows:

The catalyst carrier was, a finely divided natural chalcedonic cryptocrystalline silica having a particle size range from 4 to 40 microns diameter, a. specific surface of 4.21 square meters per gram as determined by the Brunauer-Emmett-Teller low temperature nitrogen absorption method, and an SiOz content of over 98 /z%, of

sulting slurry was agitated for one hour and filtered; The filter cake was reslurried, refiltered, and washed until the sequence had been repeated four times. The washed filter cake was dried at 100-110 C. and ground to pass through an 80-mesh screen. 4470 parts of green catalyst comprising silica particles coated with basic nickel carbonate were obtained.

Dried "green catalyst (1030 parts) was charged to an igniter and heated to 50 C. Ammonia synthesis gas (a mixture of circa 75% H2 and 25% N2 was passed through the igniter at about p. s. i. g. during a 7 hour heat up to 400 C. and a 4 hour reaction period at 400 C. The ignited catalyst comprising metallic nickel on silica was cooled to 55 C; ina synthesis gas atmosphereandmaintained in such atmosphere; until used.v

The additive for restoring the activity of;the nickelhydrogenation catalystwas a nickelsaltof keryl benzene sulfonic acid, called nickel Nacconol, prepared as follows:

A refined higher alkylbenzene (keryl benzene) was prepared in a manner similar to that described in U. S. P. 2,364,782 by chlorinating a kerosene fraction of petroleum distillate, condensing the resulting chlorination. product with benzene in the presence of anhydrous aluminum chloride; separating the alkylbenzene containing oil from the condensation reaction mixture by decantation; and recovering an alkyl benzene mixture byfractional distillation of the oil.

The kerosene fraction had a boiling range from about 19 to 251 C. and consisted predominantly of C12-C14 paraffin and naphthene hydrocarbons. The resulting keryl benzene had an average molecular weight of 260 to 265.

4600 parts of keryl benzene were agitated for 30 minutes at 38 to 42 C. with 846 parts of sulfuric acid. The mixture was allowed to stratify. The lower acid layer was drawn ofi. The resulting acid extracted oil was charged with 6450'parts of 100% sulfuric acid. The mix-.

ture was agitated for one hour at 58-60 C., diluted with 460 parts cold water, agitated-for 15 minutes, and allowed to settle outfor-2 /2 hours. The lower layer of spent acid was withdrawn. The resulting crude keryl benzene sul fonic acid was agitated for 15 minutes at 64 C. with 276.

nickelous keryl benzene sulfonate or nickel N'acconol' until completion of reaction was indicated by a neutral pH'test and the presence of undissolved excess nickel carbonate. The batch was filtered. The filtrate was dried to recover the. product.

22 consecutive batches of phenol were hydrogenated in an agitated pressure vessel charged with molten phenol and 860 pounds of nickel-on-silica catalyst prepared as described in the fore part of this example. The-pertinent results of these hydrogenation reactions are summarized in Table l.

The molten slurry of phenol and catalyst was agitated at -150" C.-mostly at about C.during hydrogenation. Ammonia synthesis gas comprising about 75 H: and 25 N2 was passed through the batch at 60 p. s. i. g. pressure and temperatures between 130 C. and

C. for the period of time indicatedin column 4. Hydrogenation was discontinued when the setting point of a sample-of thebatch reached a satisfactory value, circa 22 or 23* C., or when the setting points of successive samples failed-to showan increase with continued hydrogenation. After hydrogenation and agitation was stopped, the batch was allowedto' settle out'for about four hours whereafter the product was decanted from the lower layer or heel of settled catalyst. The next batch of molten phenol was then charged and-processed. Nickel Nacconol was added'to the first batch to assist in decontaminating. the hydrogenation equipment, which was new. New equipment is prone to contaminate catalyst and give erratic resultssothjat it is often necessary to sacrifice the product and/or catalyst used in the first batch until the equipment hasbeen broken in.

The catalyst lost activity during batch No. 5 (as evidenced by a cyclohexanol setting point of 8 C.) and went completely dead during batch No. 6. Samples of dead catalyst were subjected to numerous laboratory tests. It was foundthat the catalyst could be used at activity levels approaching theoriginal value if nickel Nacconol was-added to the reaction medium. This result was surprising because it was unsuspected that nickel Nacconol or any other similar ordissimilar substance had a remedial power to undo the effects of catalyst poisoning when used in situ during processing.

Accordingly 15 lbs. of nickel Nacconol were added to batch No. 6, which was finished successfully as to hydrogenation time and product quality. The hitherto dead catalyst was thereafter used at normal activity levels for 16 successive batches.

Catalyst selectivity fell off at batch 14 when the maximum setting point of cyclohexanol product obtained was 185 C. This was the culmination of a trend of successively lower setting points occurring through batches 9 to 14 inclusive. Addition of 5 lbs. of nickel Nacconol to batch 15 caused a reversal of this trend and enabled the catalyst to be used successfully for 6 more batches.

Further experience with the process of this example has shown that use of nickel Nacconol makes it possible to hydrogenate about 33 batches of 22,000 gallons phenol each to a cyclohexanol product having a setting point averaging above 23 C. with a single charge of 350 lbs. of ignited nickel-on-silica catalyst. Nickel Nacconol is added when a fall off of catalyst activity occurs as indicated by low setting point of product. Usually this occurs but once in a batch and between batch and batch 20. Addition of nickel Nacconol to the first batch is not necessary, although it may be useful when new equipment is used for the first time. Moreover the final loss of catalyst activity results in part from a cumulative loss of catalyst in the decanted product; this loss amounts on the average to about 5 lbs. of catalyst per batch. It is advantageous to recover this catalyst as a concentrated catalyst-in-cyclohexanol slurry by passing the decantate through a cream-separator type centrifuge. By combining use of nickel Nacconol to maintain catalyst activity with centrifugal separation of decanted catalyst, it is possible to use the catalyst for an indefinitely prolonged period far surpassing that obtainable by prior art methods. For example, Brochet, Comptes Rendus (Par-is), volume 175, pp. 5 835 (1922) reports that an unsupported nickel catalyst used in phenol hydrogenation by a process similar to that of this example lost its activity after use in nine successive batches.

Table 1 USE OF NICKEL NACCONOL TO RESTORE ACTIVITY OF DEAOTIVATED NICKEL HYDROG-ENATION CATALYST Product Setting Point,

hours C.

Nickel Nacconol Charged,

pounds Phenol charged, gallons Hydro- Batch No. genation Tim 'mmmterowww row w s st s we fiww i i f e 1 Mechanical defects in agitation equipment necessitated a reduction in phenol charge in this and most subsequent batches.

2 Charge material was partially hydrogenated phenol condensed from efiiuent gas of other units and here reprocessed.

EXAMPLE 2 In'this example the restorative effects of various additives on the activity of spent phenol hydrogenation catalyst are compared.

Fresh catalyst in the control experiments was prepared as described in the fore part'of; Example 1. The spent catalyst used to evaluate the additives was a homogeneous composite of the same type of catalyst which had had its activity impaired by prolonged use in the hydrogenation of phenol as described in Example 1.

The nickel Nacconol additive tested was prepared as described in Example 1. The Nacconol salts of copper, silver, iron and cobalt tested were prepared by a similar procedure from the following starting materials: cupric carbonate containing a small amount of cupric hydroxide; silver hydroxide; ferrous hydroxide and cobaltous hydroxide. The same general procedure was also used to prepare nickelous benzene sulfonate and nickelous toluene sulfonate by addition of basic nickel carbonate to aqueous benzene sulfonic acid or toluene sulfonic acid. The cobaltous naphthenate tested was a commercial product containing 6% cobalt and vended under the name Nuolate by Nuodex Products Inc. of Elizabeth, N. J.

The nickelous Lorol sulfate was prepared by use of Lorol No. 5, a mixture of straight chain normal alcohols marketed by E. I. du Pont de Nemours and Co., and

comprising 2.6% of decyl alcohol, 61.0% lauryl alcohol (dodecanol-l), 23.0% of myristyl alcohol (tetradecan- 01-1), 11.2% of cetyl alcohol (hexadecanol-l) and 2.2% of stearyl alcohol (octadeca11oll). This mixture of alcohols was reacted with chlorosulfonic acid to obtain a corresponding mixture of monoalkyl sulfates. These were neutralized with basic nickelous carbonate in aqueous medium of the neutral neutralization technique, i. e. increments of Lorol acid sulfate and basic nickel carbonate were successively added to the medium to keep the pH at between 6.5 and 7. The resulting solution was filtered and evaporated to recover the product.

The tests were carried out at 145 C. and atmospheric pressure, with agitation, in experimental hydrogenation equipment. The hydrogenator charge consisted of a phenol, 5% by weight on the total charge of catalyst, 0.8% by weight on the total charge of additive (where used) and 1% or 1.2% by weight on the total charge of sodium carbonate (where used).

Table 2 summarizes the restorative effect of various additives on the activity of spent hydrogenation catalyst.

Table 2 gives the average rate of hydrogen absorption in standard cubic feet per hour for each test. Hydrogen consumed by the reaction was measured for the four hour period following the time the batch reached reaction temperature.

Table 2 gives the relative activity of the catalyst under test conditions compared to the activity of fresh catalyst. The relative activity is calculated by the formula Average hydrogen absorption Average hydrogen absorption of fresh catalyst Table 2 gives the relative activity of the additive in terms of a standard activity value of 100 for nickel Nacconol. The relative activity of the additive is calculated by the expression Average hydrogen ab- Average hydrogen absorpsorption of test tion with spent catalyst Average hydrogen absorption Average hydrogen with spent catalyst andabsorption with nickel Nacconol spent catalyst and (4) cupric Nacconol, cobaltous Nacconol, cobaltous naphthenate and ferrous Nacconol are catalyst poisons which stop the reaction entirely.

Table 2 ES QRAT E EFEE OT F, ARLQUS; ADDlEIl/ES: ON THE ACTIVITY OF SPENT HYDRQGENATION CATALYST H2 Absorp- Relative Relative Catalyst Percent Additive tion Rate, Activity Activity NaiOOa s. e; f./hr. of Oataof Addilyst tive Fresh 1. 0 0. 3

1.0 d0 0.07 1. 0 N ickelous Nacconol 0. 28 1. 0 Nickelous Lorol Sulfate 0.39 l. 0 Silver NacconoL... 0.2 1.0 Ferrous Nacconol. 1.0 1. 0 1. O 1.2 0. 31 1. 2 0. 06' l. 2 0. 28 None 0. 36 None 0; 08 N one 0. 29 None 0 10 1 System poisoned.

Although certain preferred embodiments of the invention have been disclosed for purpose of illustration, it will be evident that various changes and modifications may be made therein without departing from the scope and spirit of the invention.

I claim:

1. A process for reactivating a nickel catalyst deteriorated by use in the liquid phase hydrogenation of phenol which comprises adding to the nickel catalyst. a metal salt of a surface active compound containing 6-30 carbon atoms, said salt having the general formula:

wherein R is an organic radical selected fromthe group consisting of hydrocarbon radicals and substituted hydrocarbon radica ls, x is l or 0, M is a member selected from the group consisting of Ni and Ag, and It stands for one of the numbers 1 and 2 and satisfies the valence of M.

2. A process for reactivating a nickel catalyst deteriorated by use in the liquid phase hydrogenation of phenol which comprises adding to the nickel catalyst a metal salt of a surface active compound containing 6-30 carbon atoms, said salt having the general formula:

wherein R is an organic radical selected from the group consisting of hydrocarbon radicals and substituted hydrocarbon radicals, x is l or 0, M is Ni, and It stands for the number 2 and satisfies the valence of M,

3. A process for reactivating a nickel catalyst deteriorated by use in the liquid phase hydrogenation of phenol which comprises adding to the nickel catalyst a metal salt of a surface active compound containing 630 carbon atoms, said salt having the general formula:

wherein R is an organic radical selected frolurthe group consisting ofhydrocarbon radicals. and substituted hydrocarbon radicals, x is 1 or O, M is Ag, 'and n stands for the number 1 and satisfies the valence of M.

4. in a process for the production of cyclohexanol by the hydrogenation of phenol in. the. liquid. state. inthe presence of a used nickel-on-silica catalyst, the improvement which comprises maintaining said used nickel-onsilica catalyst at high activity by the addition of a metal orated by use in the liquid phase hydrogenation of phenol which comprises adding to the nickel catalyst a nickel salt of an alkane sulfonic acid containing 63() carbon atoms.

6. Aprocess for reactivating a nickel catalyst deteriorated by use in the liquid phase hydrogenation of phenol which comprises adding to the nickel catalysta nickel salt of a sulfated alcohol containing 630 carbon atoms.

7. A process for reactivating a nickel catalyst deteriorated by use in the liquid phase hydrogenation of phenol which comprises adding to the nickel catalyst a. nickel.

salt of an aromatic sulfonic acid containing 6-30 carbon atoms.

8. A process for reactivating a nickel catalyst deteriorated by use in the liquid. phase hydrogenation of phenol which comprises adding to the nickel catalyst a nickel salt of an alkyl aromatic sulfonic acid containing 6-30.-

carbon atoms.

9. A process for reactivating a nickel catalyst deteriorated by use in the liquid phase hydrogenation of phenol which comprises adding. to the nickel catalyst. a. nickel.

salt of 'an aralkyl sulfonic acid containing 6-30-carbon atoms.

10. In a process for the hydrogenation of phenol'in the liquid state in the presence of a usedv nickel. catalyst,

the improvement which comprises maintaining'said-used nickel catalyst 'athigh activity by the addition of a metal:

salt of a surface active compound containing 6-30 car. bon atoms, said salt having the general. formula:

a-(mr l-o- M wherein R is an organic radicalselected from the group consisting of hydrocarbon radicals and substituted hydrocarbon radicals, x is l or 0, M is a member selected from the group consisting of Ni and Ag, and it stands for one of the-numbers 1 and 2 and. satisfies thevalence of M.

No references cited. 

1. A PROCESS FOR REACTIVATING A NICKEL CATALYST DETERIORATED BY USE IN THE LIQUID PHASE HYDROGENATION OF PHENOL WHICH COMPRISES ADDING TO THE NICKEL CATALYST A METAL SALT OF A SURFACE ACTIVE COMPOUND CONTAINING 6-30 CARBON ATOMS, SAID SALT HAVING THE GENERAL FORMULA: 